Recipient vessels for free flaps in advanced facial oncologic defects

Highlights • Advanced oncologic defects of midface and scalp are challenging for reconstruction.• Free ﬂaps in the midface and scalp region are the gold standard for advanced cases.• No consensus in the literature on the best recipient vessels for microanastomosis.• Superficial temporal and cervical vessels are reliable options for microanastomosis.


Introduction
Advanced oncologic defects of the midface and scalp are a significant challenge to the reconstructive head and neck surgeon, who must consider the need for midfacial projection, rehabilitation, and function restoration. Soft free tissue flaps, such as anterolateral thigh flaps, latissimus dorsi myocutaneous flaps and rectus abdominis flaps are excellent reconstructive options for advanced cases, adequately repairing large defects and filling dead spaces. 1---5 One important aspect of using free tissue flaps in the midface and scalp region is the choice of the recipient vessels for the microanastomosis. Cervical vessels are often the first option in head and neck reconstruction, especially when the lower third of the face is involved. However, if recipient vessels in the neck are selected for midface and scalp reconstruction, a long vascular pedicle must be harvested. In addition, the surgical team should take into consideration the history of previous neck dissection or prior radiotherapy, which can compromise the outcome of microanastomosis. For these cases, the superficial temporal vessels could be used as a recipient target, due to their ideal location and straightforward dissection. 6---9 The superficial temporal vessels have been shown to have comparable diameters to the cervical vessels, with increased proximity to defects in the midface and scalp. Yet, because of their variable diameter and tortuous anatomy, these vessels have been considered to be at risk for postoperative vasospasm and thrombosis, and its use has been restricted to selected cases. 10,11 The aims of this study are to demonstrate a prospective study in midface and scalp advanced oncologic reconstruction using free tissue flap and to compare the postoperative outcomes based on superficial temporal versus cervical recipient vessels.

Methods
We performed a parallel group clinical trial in patients who underwent midface and scalp reconstruction with free tissue flaps in the department of head and neck surgery of the Brazilian National Cancer Institute from April 2018 to April 2022. This study was approved by the IRB of the Brazilian National Cancer Institute and registered in an international clinical trials database (ClinicalTrials.gov identifier: NCT05749120). All participants signed an informed consent form. The following inclusion criteria were employed: (1) Patients eligible to subtotal, total, or extensive radical oncologic maxillectomy, or advanced scalp oncologic resection; (2) Patients with clinical conditions suitable for major surgery; (3) Complete medical records. Patients were randomized into two groups by the main author in blocks of four patients for each technique (one to one ratio) who were blinded to the intervention, namely Group A: the superficial temporal recipient vessels; and Group B: the cervical recipient vessels. Patient gender and age, cause and classification of the defect, flap choice for reconstruction, recipient vessels, postoperative course, and complications were recorded and analyzed. Patients who died within a period of less than 30 days of the surgical intervention or who missed follow-up for a period of less than 3 months were excluded.

Statistical analysis
Sample-size estimation was performed using OpenEpi (openepi.com). In Brazil, the estimated incidence of nonmelanoma advanced skin cancers that affect the midface and scalp and are eligible for surgery is 800 cases/year (see https://www.gov.br/inca/pt-br/assuntos/cancer/numeros/ estimativa consulted in 02/18/2023). We estimated a sample-size of 26 patients with 95% confidence level. Considering an attrition rate of 20%, we set the sample-size at 32 patients. A Fisher's exact test was used to compare outcomes between the 2 groups. The p < 0.05 was considered statistically significant.

Results
Thirty-two patients were selected and randomized into two groups. Five patients were excluded from the study. The total study period was developed prospectively over 4 years (from April 2018 to April 2022) with the recruitment period occurring during the initial 45 months. The minimum followup of the patients was 3 months, enough time to assess major and minor complications. The diagram describes the participants flow (Fig. 1). Twenty-seven patients were analyzed: Group A with superficial temporal recipient vessels (n = 12) and Group B with cervical recipient vessels (n = 15).     In Group B, the following recipient arteries were used: facial artery (n = 9), superior thyroid artery (n = 4), and lingual artery (n = 2). The recipient cervical veins used in this group were: facial vein (n = 11) and internal jugular vein (n = 4). Vein grafts were not used. All microanastomosis were performed in an end-to-end fashion except for four cases, in which the anastomosis with the internal jugular vein were performed using an end-to-side technique. Only one patient in Group B required early return to the operating room due to microvascular vascular anastomosis obstruction, with successful resolution. Arterial thrombosis developed in one patient in Group B on the 2nd postoperative day, with total flaps loss. Two patients in Group A suffered total flap loss: one due to venous thrombosis on the 3rd postoperative day, and one due to arterial thrombosis on the 5th postoperative day. Both patients underwent a late successful reconstruction with another free tissue flap. No other major complications occurred in this group.
In the present series, the overall flap survival rate was 88.89% (24 of 27 flaps). All major complications involved microvascular thrombosis, with a complication rate of 14.81% (4 of 27 patients). Of the three patients who developed total flap loss, two were in Group A (16.67%) and one was in Group B (6.66%), not significant (p = 0.56). Minor complications such as seroma, partial dehiscence or infection occurred in 5 patients (18.51%). There was no statistically significant difference in the comparison between groups (p = 0.342). The vascular pedicle length of the free tissue flap of Group A was 11.75 ± 2.30 cm, while in Group B the vascular pedicle length of the free tissue flap was 10.67 ± 2.13 cm (p = 0.216). The characteristics of the technical aspects and complications of free flaps in both groups are listed in Table 2.

Discussion
Few articles have specifically compared the postoperative results based on the choice of the recipient vessels in midface and scalp microvascular reconstruction. 12---14 One of the most important factors for the selection of the recipient vessels is the distance from the flap inset location. In our study, the distance among the advanced oncologic defects and the recipient vessels was not significant, probably because we selected free tissue flaps with long vascular pedicle as anterolateral thigh flaps, latissimus dorsi myocutaneous flaps, rectus abdominis flaps and forearm flaps. 5---7 The average length of the main pedicle of our series was nearly 11 cm, considered adequate tension-free safe anastomosis using either the superficial temporal or the cervical vessels. Anatomically, the superficial temporal vessels are substantially closer to the midface and scalp region than the cervical vessels. Theoretically, this proximity could facilitate the reconstruction, with no need for a vein graft. In fact, in the present series, all microanastomosis were performed primarily, and no vein graft was necessary. We believe that this option decreases time of surgery and reduce the rates of vascular complications associated with vein grafts.
The superficial temporal vessels are readily available, and their suitability as recipient vessels for microvascular free tissue flap in head and neck reconstruction has been reported by numerous authors. 14--- 16 The major drawback to their use is the tortuous nature of the vessels in this location, their perceived tendency to vasospasm, given their superficial nature, and the concern for proximity to the facial nerve. To improve results and minimize these vascular complications, some authors have describe a dissection even more proximal into the intraparotid segment of the superficial temporal vessel. 17 Another consideration is that the inset location or positioning, as well as the ultimate reconstructive results, could potentially be influenced by limitations of the vascular pedicle. When using the superficial temporal vessels, however, the length of the vascular pedicle does not need to be nearly as long. This, in turn, makes it easier to tailor the reconstruction of the composite 3-dimensional defects of the midface and scalp.
Although there was no significant difference in the rate of total flap loss between the 2 groups in our series, the rate of complications was nevertheless higher in patients with superficial temporal recipient vessels than in those with cervical recipient vessels. It is important to emphasize that, of the 4 patients who had microvascular anastomosis complications, three were undergoing secondary free tissue flap reconstruction, due to previous total flap loss. In our series, the overall flap survival rate was 88.89%. These data are similar to other available series reporting above 90% of success in free flaps for advanced cases. 7,18 In cases in whom a secondary reconstruction is performed, cervical vessels are often inadequate or absent; moreover, they are frequently encased in scar tissue due to previous neck dissection or radiotherapy. In this situation, the superficial temporal vessels are probably a better choice, not only because they are anatomically closer, but rather they have not been affected by any previous treatment. In our series, only 4 patients underwent secondary reconstruction; all individuals had already been submitted to either radiotherapy and/or neck dissection. Despite an additional technical difficulty at the cervical preoperative site, this finding did not preclude the performance of a successful microanastomosis.
Wang et al. 19 reviewed the advantages and disadvantages of using free flaps for anterior skull base defects using both superficial temporal and cervical recipient vessels. They concluded that, depending on the extent of the resection and the length of the vascular pedicle of the free flap, both options are reasonable. Our study demonstrated that both cervical and superficial temporal recipient's vessels proved to be viable options for the microvascular reconstruction of extensive midface and anterior skull base oncologic defects. We agree with Yazar 20 that the superficial temporal vessels should be the preferred recipient vessels for microvascular anastomosis in secondary free flap reconstruction, as they are usually located far from the previous surgical dissection. Furthermore, Imanishi et al. 21 showed that the superficial temporal vein has a complex pattern with numerous branches and connections. These factors make the superficial temporal vein a safe option for dissection and anastomosis, even if the ipsilateral internal jugular vein is ligated. Hansen et al. 22 described their successful experience with the superficial temporal vessels as recipient vessels for facial and scalp reconstruction.
Our study is not without limitations. First, selection bias could have been an issue, since the main author did patient allocation. Even though, we cannot completely exclude this systematic error, our statistical results indicate that groups were similar in each and every domain, so minimizing the effect of patient selection. Finally, sample size is not expressive, but proved adequate on statistical analysis. It is worth considering the rarity of such advanced cancers of the midface and scalp, even in reference centers, like ours, resulting in very large surgical defects and demanding very complex reconstructions. Our results should be validated in large multicenter studies. On the other hand, our study is the first randomized study in the field providing further support for the use of superficial temporal vessels in such difficult cases of midface and scalp advanced oncologic reconstruction.

Conclusion
Midface and scalp advanced oncologic reconstruction using cervical or superficial temporal recipient vessels did not differ in terms of success and complication rates. Therefore, the use of superficial temporal recipient vessels may be a reasonable option, especially in a secondary reconstruction setting.

Funding
The study had own financing.

Conflicts of interest
The authors declare no conflicts of interest.